Oxygen deficiency alarm



y 1958 J. w. BOGDANQWSKI ET AL 2,835,886

OXYGEN DEFICIENCY ALARM Filed May 2, 1956 5 mu My 54 2 1 Han ii 21 5 I 14 27 l I 14 18 44 my I. I l j 1 1 2'1 25 5:233:34? Z1 16 4'2 41 INVENTORS.

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By CH4 R'LES [flu TTU.

United States Patent @t OXYGEN DEFICIENCY ALARM John W. Bogdanowski, Flushing, and Charles Kiuttu, New York, N.- Y., assignors to Consolidated Edison Company of New York, Inc., New York, N. Y., a corporation of New York Application May 2, 1956, Serial No. 582,160

2 Claims. (Cl. 340-428) This invention relates to an oxygen deficiency alarm and more particularly to improvements in apparatus for audibly detecting a deficiency of oxygen in the atmosphere surrounding a flame.

One of the first devices taking advantage of the condition of a flame for detecting a deficiency of oxygen in the atmosphere was the safety lamp invented by Sir Humphrey Davy. By visually observing the small flame of this lamp, one is able to detect a deficiency of oxygen through reduction in the flame size, and also to detect the presence of a combustible mixture in the atmosphere by an increase in the size of the flame. The Davy lamp has been used successfully without substantial changes for well over a century. It is particularly well adapted because of its small size and portability for use in underground conduits and manholes. However, it is subject to the limitation that to be advised of the oxygen content of the air in the confined space, it is necessary that those working therein maintain a close watch over the flame. This necessity for visual inspection of course impairs the workers efficiency. Furthermore, in certain underground operations, such as the splicing of electrical cables, the deficiency of oxygen might well result from the escape into the confined air space of some other gas under pressure, such as nitrogen, which is commonly employed as an inert surrounding for electrical conductors within a cable. Experience has shown that inhalation of air of unusually high nitrogen content, while not immediately fatal, very quickly impairs the mental processes involved in muscular mobility, making it diflicult for the person so affected to escape from the confined space. Thus, a device for detecting decreases in the oxygen concentration should be very sensitive. The Davy lamp and its counterparts are sufficiently sensitive, but they are open to the serious objection that they must be constantly watched. Accordingly, a device employing the proved design of the Davy lamp, but transforming the information regarding oxygen deficiency relayed by the flame to an audible alarm, thus obviating visual inspection, would be highly desirable.

In an attempt to successfully and practicably solve the problem, several well-known temperature-sensitive devices and allied alarm circuits have been employed in conjunction with the Davy lamp. For example, a metal bulb, capillary tube and bellows assembly relying upon the expansion and contraction of gas within the bulb to open and close a micro-switch has been tried. Similarly, a bimetallic thermostat which closes an electrical contact on cooling, as well as thermistors, i. e., resistors with a high negative temperature coefficient of resistance which experience a large change in resistance with small changes in temperature, have been employed. Each of these three temperature-sensitive devices has proved unsatisfactory as means for actuating the alarm when the oxygen in the atmosphere surrounding the flame has been reduced to a point dangerous to life, because of the excessive time lag caused by the slow cooling of the lamp mass before the alarm is sounded.

2,835,886 Patented May 20, 1958 In accordance with the present invention, apparatus is provided in conjunction with the safety lamp, including an alarm-actuating crystal photo-cell sensitive to changes in radiant energy, as distinguished from the heat energy, output of the flame. Associated with this cell is the requisite current amplifying alarm circuit. More specifically, the apparatus may include a shade for the chimney of the lamp, which shade has at least one perforation through which radiant energy from the flame is directed onto a crystal photo-cell, and preferably from the flame axis or an upward extension thereof. There is also provided a suitable housing externally of the shade for the crystal photo-cell. The cell. is of such a character as to be responsive to and conducting in the presence of the radiant energy emitted by the flame burning in air. As the radiant energy output of the flame decreases through reduction in flame size caused by a deficiency of oxygen in the area surrounding the flame, the crystal photo-cell becomes sufllciently less conductive to actuate its associated alarm. The alarm is desirably an audible device such as a hell or buzzer. However, it may also consist of a warning light alone or in association with the audible means. The circuit may be so arranged as to actuate an alarm in the immediate vicinity of the lamp and also at a chosen remote control point.

In the drawings:

Fig. 1 is a fragmentary perspective, partially cut away view of a safety lamp to which there is attached a portion of the apparatus of the present invention;

Fig. 2 is a perspective of a lamp similar to that of Fig. 1, illustrating a modification of the apparatus of the present invention;

Fig. 3 is a vertical section through the photo-cell housing, a portion of the lamp shade and glass chimney;

Fig. 4 is a perspective view of a plastic-encased photocell; and

Fig. 5 is a diagram of a preferred photo-cell alarm circuit.

Referring first to Figs. 1 and 2, there is illustrated a conventional safety lamp with a fuel tank base 11, a support ring 12, support rods 13, a strengthening ring 14, corrugated shield 15 as well as a cylindrical glass chimney 16 surrounding flame 17. In accordance with the present invention, the lamp is provided with a cylindrical shade 18, preferably of metal, which completely surrounds chimney 16. The shade is perforated as at 19 with the periphery of the hole flanged to form a hollow shade extension tube 21, threaded as at 22 (Fig. 3) or similarly adapted to receive a photo-cell housing 23, which is detachably positioned at the end of extension tube 21 by a collar 27. A crystal photocell 24, encased in plastic material 26', together with its lead Wires 29 and 29a is disposed within housing 23 so that the transparent end .23 (Fig. 4) of cell case 26' is directed through the interior 20 of tube 21 toward the interior of the lamp and the area of the flame 17. The housing 23 is suitably adapted at its outer end as by a spring 31 to prevent fraying of the photo-cell lead wires.

The shade 18 is cut away as at 32 to provide at least one port for visual observation of the lamp flame. The port is preferably so disposed as to prevent extraneous radiant energy from directly striking the transparent end 28 of the photo-cell.

The photo-cell is directed at the axis of flame 17 and in the lamp of Fig. 1, its position normal to this axis is fixed. Preferably, the wick of the lamp is so adjusted that cell 24 is directed at the upper portion of the flame. It is important that the shade 18 be of a material which will not transmit energy of the Wave length emitted by the flame, in order that the photo-cell be responsive only to radiant emissions of the flame. If the shade were of transparent material, extraneous radiation, visible or 2,sezs,sse

infra-red for example, might influence the photo-cell to such an extent that it would be possible for the flame to be reduced in size or even extinguished by reason of a deficiency of oxygen and yet the alarm would not sound because the photo-cell continued to be conducting. In operation of the apparatus of Fig. 1, with the cell in a fixed position relative to the flame, the sensitivity of the device may in part be regulated by changing the height of the flame.

Referring now to Fig. 2, it will be observed that the shade 18 is slidable vertically, and is provided with a rack 41. Support ring 12 is adapted to receive the journal end of a shaft 42 hearing a worm gear 43, which engages rack 41. By rotation of the knurled thumb screw 44 atop shaft 42, the shade 18 may be raised or lowered. This adjustment may be used substantially to increase the sensitivity of the apparatus. For example, if it is desired that the device be particularly sensitive, the shade is elevated so that the photo-cell is directed at the uppermost part of the flame, or, if the cell is infra-red-sensitive, the shade might be elevated still farther so that the cell is directed at the space above the flame. Under these conditions, a very slight reduction in flame size by reason of a slight reduction in oxygen content of the surrounding air results in a reduction of infra-red radiation sufiiciently great to render the cell non-conducting, and thus sound the alarm. It will be apparent that as an alternative to the slidable shade of Fig. 2, the same degree of sensitivity may be achieved with a fixed shade having only a vertically slidable extension tube portion for the cell.

We have found that crystal photo-cells sensitive to infra-red radiations are far superior to conventional selenium cells relying upon visible light to develop a current. the flame of safety lamps of the character above described and illustrated is not sufliciently great, even with the interposition of a magnifying lens between flame and cell to cause the cell to develop a sufliciently high and reliable current to properly operate the alarm circuit. As indicated, crystal photo-cells sensitive to infra-red radiation are preferred, and one manufactured by Clairex Corporation, New York, New York, known to the trade as CL-Z, which has a high response to infra-red radiation of the wave lengths between 5200 and 7500 Angstrom units, is particularly satisfactory.

In Fig. there is illustrated a preferred electrical circuit for providing an audible signal when the flame decreases below a predetermined level. The circuit shown in Fig. 5 comprises a transistor 46 having a base electrode 47, a collector electrode 48 and an emitter electrode 49. The photo-cell 24 is connected between the base electrode 47 and the emitter electrode 49 by a lead 5% a switch 51, a battery 52, a lead 53, a variable resistor 54, and a potentiometer 55, one end of which is connected to the emitter electrode 49 and the other end of which is connected to a resistor 56. The potentiometer 55 and the resistor 56 are connected in parallel with a battery 57 by means of a lead 58 and a switch 59. Adjustment of the arm 60 of the potentiometer 55 adjusts the voltages applied to the electrodes of resistor 56 and hence varies the operating conditions and the currents in the various circuits connected to the electrodes.

The energizing coil 61 of a relay 62 is connected between one end of the resistor 56 and the collector electrode 48 so that the relay 62 is energized by the current flowing between the base electrode 47 and the collector electrode 48. The relay armature 63 is shown in Fig. 5 as pulled up against the front contact 64 and hence the armature 63 is in the position it assumes when the coil 61 is energized as hereinafter described. Normally, the armature 63 rests against the back contact 65 and may be pulled thereagainst by a spring 66. When the armature 63 rests against the contact 65, the circuit for Generally speaking, the visible light output of the energization of a bell or buzzer 67 is completed by Way of a lead 68, the coil 69 of the bell or buzzer 67, a battery 70, a switch 71, and a lead 72. A shunt path for testing the bell or buzzer 67 is provided by a lead 73 and a switch 74. When the switch 74 is closed manually, the bell or buzzer 67 is energized and hence, if the battery has the correct voltage, and the hell or buzzer is in proper condition, the latter is operated.

The switch 51 serves to complete the circuit between the emitter electrode 49 and the base electrode 47, whereas the switch 59 serves to complete the energizing circuit for the collector electrode 48. A switch 71 prepares the energizing circuit for the bell or buzzer 67 for Operation by the relay 62. Switches 51, 59 and 71 are manually operable and, as indicated in Fig. 5, these switcles are preferably ganged together.

When the circuit is energized by manually closing switches 51, 59 and 71, the current flow between the emitter electrode 49 and the base electrode 47 will control the current flow between the collector electrode 48 and the base electrode 47. The current flow between the emitter electrode 49 and the base electrode 47 is controlled by the potentiometer 55, the resistor 54 and the voltage developed by the photo-cell 24 by the impingement of radiant energy thereon. After the switches 51, 59 and 71 are closed manually, the flame 17 is adjusted to the desired height which may be indicated by markings on the chimney 16, the lamp being operated in an atmosphere having the proper oxygen level. The radiant energy from the flame 17 will energize the photo-cell 24 and the arm 66 of the potentiometer is adjusted until the current flowing in the coil 61 is slightly more than that required to draw the armature 63 up against the contact 64. The resistor 54 is then adjusted until the desired current through the photo-cell 24 and the desired operating conditions are obtained. Of course, as will be understood by those skilled in the art, adjustment of the resistor 54 may require readjustment of the arm so that the armature 63 will fall back against the contact and operate the bell or buzzer 67 when the size of the flame 17 decreases to a predetermined value. Since the voltage developed by the photo-cell 24 and hence the current through the coil 61 varies with the size of the flame 17, a decrease in the flame size producing a decrease in the current in the coil 61 and vice versa, it will be apparent that by proper adjustment of the arm 60 and the resistor 54, the bell or buzzer 67 may be caused to operate when the flame decreases in size due to a dangerous deficiency or a decrease in oxygen level.

Although certain particular embodiments of the invention are herein disclosed for purposes of explanation, various further modifications thereof, after study of this application, will be apparent to those skilled in the art to which the invention pertains. Reference should accordingly be had to the appended claims in determining the scope of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. In a safety lamp for detecting a deficiency of oxygen in the atmosphere surrounding the lamp flame sufficiently great to impair mental processes and endanger human life, means for audibly detecting slight reductions in flame size resulting from reduction in the oxygen content of the atmosphere, consisting of a vertically slidable, infra-red impermeable shade enclosing said flame, said shade having a perforation in its side, a crystal photo-cell responsive to and conducting in the presence of the infra-red radiations, including radiations of a wave length of about 5200 to 7500 Angstrom units emitted by the flame burning in air positioned at said perforation and directed at the axis of the flame, means surrounding said crystal photo-cell and detachably engaging said shade for retaining the cell in the aforementioned position, an amplifying circuit for said cell, audible alarm means in said circuit which when said cell is conducting are inoperative, and means associated with the lamp body and shade for adjusting the shade in a direction substantially parallel to the axis of the flame.

2. In a safety lamp for detecting a deficiency of oxygen in the atmosphere surrounding the lamp flame sufiiciently great to impair mental processes and endanger human life, means for audibly detecting slight reductions in flame size resulting from reduction in the oxygen content of the atmosphere, consisting of an infrared irnpermeable shade enclosing said flame, said shade having a portion thereof slidable along the axis of the lamp flame, said portion having a perforation therein, a crystal photo-cell responsive to and conducting in the presence of the infra-red radiations, including radiations of a wave length of about 5200 to 7500 Angstrom units, emitted by the flame burning in air positioned at said perforation and directed at the axis of the flame, means surrounding said crystal photo-cell and detachably en said shade for retaining the cell in the aforementioned position, an amplifying circuit for said cell and audible alarm means in said circuit which when said cell is conducting are inoperative.

l ieficrences Cited in the file of this patent UNITED STATES PATENTS 2,567,036 Shannon Sept. 4, 1951 

1. IN A SAFETY LAMP FOR DETECTING A DEFICIENCY OF OXYGEN IN THE ATMOSPHERE SURROUNDING THE LAMP FLAME SUFFICIENTLY GREAT TO IMPAIR MENTAL PROCESSES AND ENDANGER HUMAN LIFE, MEANS FOR AUDIBLY DETECTING SLIGHT REDUCTIONS IN FLAME SIZE RESULTING FROM REDUCTION IN THE OXYGEN CONTENT OF THE ATMOSPHRE, CONSISTING OF A VERTICALLY SLIDABLE, INFRA-RED IMPERMEABLE SHADE ENCLOSING SAID FLAME, SAID SHADE HAVING A PERFORATION IN ITS SIDE, A CRYSTAL PHOTO-CELL RESPONSIVE TO AND CONDUCTING IN THE PRESENCE OF THE INFRA-RED RADIATIONS, INCLUDING RADIATIONS OF A WAVE LENGTH OF ABOUT 5200 TO 7500 ANGSTROM UNITS EMITTED BY THE FLAME BURNING IN AIR POSITIONED AT SAID PERFORATION AND DIRECTED AT THE AXIS OF THE FLAME, MEANS SURROUNDING SAID CRYSTAL PHOTO-CELL AND DETACHABLY ENGAGING SAID SHADE FOR RETAINING THE CELL AND DETACHABLY ENTIONED POSITION, AN AMPLIFYING CIRCUIT FOR SAID CELL, AUDIBLE ALARM MEANS IN SAID CIRCUIT WHICH WHEN SAID CELL IS CONDUCTING ARE INOPERATIVE, AND MEANS ASSOCIATED WITH THE LAMP BODY AND SHADE FOR ADJUSTING THE SHADE IN A DIRECTION SUBSTANTIALLY PARALLEL TO THE AXIS OF THE FLAME. 